Documentation/devicetree/bindings/soc/fsl/cpm_qe/cpm.txt

Source file repositories/reference/linux-study-clean/Documentation/devicetree/bindings/soc/fsl/cpm_qe/cpm.txt

File Facts

System
Linux kernel
Corpus path
Documentation/devicetree/bindings/soc/fsl/cpm_qe/cpm.txt
Extension
.txt
Size
2279 bytes
Lines
68
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

NOTE: This is an interim binding, and will likely change slightly,
as more devices are supported.  The QE bindings especially are
incomplete.

* Root CPM node

Properties:
- compatible : "fsl,cpm1", "fsl,cpm2", or "fsl,qe".
- reg : A 48-byte region beginning with CPCR.

Example:
     cpm@119c0 {
	#address-cells = <1>;
	#size-cells = <1>;
	#interrupt-cells = <2>;
	compatible = "fsl,mpc8272-cpm", "fsl,cpm2";
	reg = <119c0 30>;
     }

* Properties common to multiple CPM/QE devices

- fsl,cpm-command : This value is ORed with the opcode and command flag
                    to specify the device on which a CPM command operates.

- fsl,cpm-brg : Indicates which baud rate generator the device
                is associated with.  If absent, an unused BRG
                should be dynamically allocated.  If zero, the
                device uses an external clock rather than a BRG.

- reg : Unless otherwise specified, the first resource represents the
        scc/fcc/ucc registers, and the second represents the device's
        parameter RAM region (if it has one).

* Multi-User RAM (MURAM)

The multi-user/dual-ported RAM is expressed as a bus under the CPM node.

Ranges must be set up subject to the following restrictions:

- Children's reg nodes must be offsets from the start of all muram, even
  if the user-data area does not begin at zero.
- If multiple range entries are used, the difference between the parent
  address and the child address must be the same in all, so that a single
  mapping can cover them all while maintaining the ability to determine
  CPM-side offsets with pointer subtraction.  It is recommended that
  multiple range entries not be used.
- A child address of zero must be translatable, even if no reg resources
  contain it.

A child "data" node must exist, compatible with "fsl,cpm-muram-data", to
indicate the portion of muram that is usable by the OS for arbitrary
purposes.  The data node may have an arbitrary number of reg resources,
all of which contribute to the allocatable muram pool.

Example, based on mpc8272:
	muram@0 {
		#address-cells = <1>;
		#size-cells = <1>;
		ranges = <0 0 10000>;

		data@0 {
			compatible = "fsl,cpm-muram-data";
			reg = <0 2000 9800 800>;
		};
	};

Annotation

Implementation Notes